This is a problem my professor assigned from the textbook: Steam at a pressure o

ID: 1861794 • Letter: T

Question

This is a problem my professor assigned from the textbook:

Steam at a pressure of 0.08 bar and a quality of 93.2%

enters a shell-and-tube heat exchanger where it condenses

on the outside of tubes through which cooling water flows,

exiting as saturated liquid at 0.08 bar. The mass flow rate of

the condensing steam is 3.4 3 105 kg/h. Cooling water enters

the tubes at 158C and exits at 358C with negligible change

in pressure. Neglecting stray heat transfer and ignoring

kinetic and potential energy effects, determine the mass flow

rate of the cooling water, in kg/h, for steady-state operation.

I determined the mass flow rate of the cooling wate to be 9.1 * 10^ (6) kg/hr which is the answer.

but.....

my professor also asked for "Find the rate of heat flow from one stream to the other as well."

the correct answer is "heat rate = 7.6 x 108 kJ/hr"

I do not know how to get the heat rate.

through the staem table

enthalpy at the inlet of condenser (h1) = 391 * .932*2273 = 2509 .4 kJ/kg

enthalpy at the outlet of condenser (h2) = 391 kJ /kg

heat flow rate = m*(h1-h2) = 3.43*10^5 *( 2509.4-391) = 7.3*10^8 kJ/hr

{ it is close to your answer ,, difference arises in answer is due to exploitation in steam table data )

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.